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13 Cards in this Set

  • Front
  • Back
-include 1 afferent (sensory) and 1 efferent (motor)
-can be diminished by pathology to:
sensory,LMN,NMJ,musc,acute UMN injury,joint disease
Sensory reflexes
-are proprioceptive or nocireceptive neurons
-neurons that directly inn. skeletal musc.
-thier cell bodies are found in:
-ventral horn of spinal cord
-axons exit by ventral roots
-crainial nerve nuclei of the brainstem
-crainial nerve 9 has motor components
-olfactory1,optical 2,hearing and balance
-LMN of brainstem exit by crainial nerve
-LMN's travel to their target via peripheral nerves
-are myelinated by schwann cells
-are A alpha or A gamma neurons
-are in command of LMNs
-include corticospinal and corticobulbar tracts
-cell bodies are in:
brainstem,cerebellar cortex,cerebral cortex,primary motor cortex(precentral gyrus)
-UMNs travel from primary motor cortex to LMNs
-if their axons terminate in brainstem=corticobulbar tract
if horn spinal cord=corticospinal tract
-they have inhibitory actions on reflexes
Classification of nerve fibers
-based on diameter and conduction velocity
Myelinated fibers:
A Alpha (Ia=spindle afferents)or(Ib=golgi tendon organ)-biggest,musc, spindle afferents, have max vel of 120m/s and diameter,
-AB (AKA 2):proprioceptive,tactile recep,max vel 70m/s
-A gamma:LMNs inn musc. spindle(intrafusal musc. fibers) max vel 30m/s
-A (sigma):some pain (sharp),max vel 30m/s
-B:lightly myelinated,max vel 15m/s,preganglionic autonomics
Unmyelinated nerve fibers
-C fibers
-postganglionic autonomics
-max vel 2.5 m/s
Deep tendon reflex and muscle spindles
-1 synapse
-sensed by musc. spindles: are encapsulated in sensory organ,interfusal fibers of alpha A afferents and A gamma efferents which maintain sensitivity of musc spindle to stretch at all lengths
Crossed flexor reflex
-pain stimuli
-2 synapses
-flexor reflex
-crossed flexor reflex which extends to opposite limb
-afferent and efferent functions
-localized skin damage
-activation occurs only if stimulus is > threshold and results in AP and afferent input to spinal cord
-some cutaneous nocioceptors have Na ch. in thier dendrites
-have AP that travels in both directions causes release of glutamate and substatnce P which results in vasodilation,and release of histamine
LMN lesions
-flaccid paralysis
-a reflexia
-development over time of musc. atrophy
-visible musc. twitches
UMN lesions
-spastic paralysis
-babinski's sign
-disease of LMN
-90% infected mild symptoms
-50% paralytic polio
-legs affected more than arms severe atrophy
-20% have brainstem involvement
-degeneration of LMN in spinal cord and brainstem
-UMN in cerebral cortex
-secondary axonal degeneration in peripheral nerves and corticospinal tract
-survival 3-4 yrs post dx
-mostly affects UMN
-if UMN damage is at the same location as LMN you get LMN symptoms
-only way you get UMN symptoms is if you have a norm UNM